Nigerian-born Rotimi Adebari (47), who was the country's first black mayor, has been dogged by the claims for the past four years.

The Portlaoise-based Independent county councillor maintains he fled his home country to come to Ireland in 2000 after coming under pressure from relatives over his conversion from Islam to Christianity.

However, several London Underground workers claim he actually worked as a train driver in the English capital in the late 1990s before moving to Ireland.

Mr Adebari denied their claims last night, saying: "My position remains the same. I stand by what I said before."

He pointed to the fact he had recently been granted Irish citizenship as proof that the claims were incorrect.

"As you are well aware, Ireland is not a country that easily gives citizenship," he said.

Mr Adebari is a candidate in the Laois/Offaly constituency. Claims about his past first surfaced shortly after he was elected mayor in 2007.

A Nigerian newspaper, 'This Day', published an article claiming Mr Adebari had not fled religious persecution.

Months later, Paddy Clarke, a retired London tube driver from Dundalk, Co Louth, came forward claiming he worked with Mr Adebari in 1999.

He said the politician had been a train operator working out of the Queens Park depot on the Bakerloo tube line.

Residency

Mr Adebari arrived in Ireland in 2000. He says he travelled directly from Nigeria, via Paris, and never worked or lived in London at any time. He applied for asylum, but the application was refused.

However, he gained automatic residency when his wife gave birth shortly after they arrived.

He did a masters degree in intercultural studies in DCU and set up a firm called Optimum Point Consultancy.

No accounts have ever been filed for the firm.

In a statement to the Irish Independent, Mr Adebari said: "We would like to point out that when any such allegation is made, one has to ask who benefits most from them."